Delay compositions for delay electric detonators



United States Patent 3,111,438 DELAY COMPOSITIONS FOR DELAY ELECTRIC DETONATORS Thomas Z. Ball, New Ringgold, and William D. Trevorrow, Tamaqua, Pa., assignors to Atlas Chemical Industries, Inc, Wilmington, Del., a corporation of Delaware No Drawing. Filed Oct. 24, 1961, Ser. No. 147,146

" Claims. (Cl. 149-37) The present invention relates to new and improved compositions for delay fuse powders of the type which comprise a mixture of inorganic oxidizing and reducing agents. The present invention also relates to a method of producing such compositions.

Delay detonators which are commonly commercially available generally consist of a tubular metal shell having one closed end, a base explosive charge, for example, pentaerythritol tetranitrate, positioned in the closed end, a primer charge or charges, for example, mannitol hexanitrate or diazodinitrophenol, positioned atop and in firing relation to the base charge, a delay element consisting of an incombustible tube containing a charge of delay fuse composition, positioned in firing relation to the topmost prime; charge, an ignition means, for example, an electric match, mounted in firing position to the delay element, and electric wires adapted to connect the ignition means to a source of electrical energy extending from the ignition means through a plug or a seal positioned in the open end of the detonator shell.

Prior to the advent of short period delay blasting techniques, blasting operations firequently employed delay detonators having delay times in increments of about one half second each. The advent of short period delay blasting techniques, wherein the delay intervals used start as low as 8 milliseconds and generally have intervals between successive delay periods in increments of from about 25 to about 125 milliseconds, brought a demand for delay fuse compositions which have a fast, reliable, and highly accurate propagation speed and which can provide short, accurate delay intervals when used in delay detonators. Hereinafter a delay detonator having such shortened delay timeswill be referred to in the present application as a short period delay detonator.

In addition to the criteria which a delay fuse composition has to fulfill to be acceptable for use in a regular delay detonator, such as good reliability, good stability, easy ignition and easy and safe manufacture, a delay composition suited for use in short period delay detonators must have a fast and highly accurate propagation speed which is not substantially altered by prolonged storage. It will be readily appreciated that the deviation from a mean detonation time in a short period delay detonator composition must be very small in order -to sharply define the respective delay periods and minimize the overlapping of one delay period with another. In addition, it is desired that the short period delay fuse composition have a sufficiently constant and fast burning speed that delay times may be accurately predicted during manufacture by measurement of the delay train length. It also is desired that the increments of powder making up the delay train length be of sufiicient size to facilitate rapid quantity production with available equipment.

The present invention provides a delay fuse composition which fulfills each of the above-discussed required and desired characteristics for a short period delay fuse composition.

According to the present invention, a delay fuse composition is provided by an intimate mixture of finely divided potassium permanganate and a fuel component made up of zinc and a member selected from the group consisting of silicon and an alloy of titanium and nickel. The alloy preferably contains between about 40 and about 80 percent by weight of titanium, about has been found to be eminently satisfactory. Preferably the composition contains a powdered zinc fuel in an amount of from about 55 to about 111% by weight of the potassium permanganate component and a second fuel in an amount of from about 3 to about 11% by weight of the potassium permanganate component. In a preferred form of the inyen-tion, the initial components are of a size that will pass a 325 mesh U.S.S. screen. The use in the present compo sition of titanium-nickel alloys containing less than about 40 or more than about percent by weight of titanium yield fuse powders which tend to have burning speeds which are difficult to predict. The inclusion of less than about 55 or over about 111% by weight of zinc as compared to the weight of potassium permanganate in the composition yields a composition which propagates burning at an undesirably low level. The inclusion of less than about 3% by weight of the second fuel component as compared to the weight of potassium permanganate yields a composition which is difficult to ignite particularly upon warm storage. The inclusion of more than ;1l% by weight of the second fuel component as compared with the weight of potassium permanganate yields a composition which has an unreliable burning speed.

A delay fuse composition of the present invention may be prepared by intimately blending the components in a finely divided form by any suitable blending procedure; suitable blending may be obtained by placing the components in a double cone blender and operating the blender for a period of about 16 hours. In order to obtain a delay fuse composition free from undesirable small particles which would make the composition difiicult to handle and which would be a.- hazard during later operations such as charging the composition into the delay tubes, the blend is preferably pelleted to obtain a pellet, and the pellet product granulated to obtain a granular product. The granulated product may then be screened to separate a powder having a grain size of between about that which will pass a 20 mesh U.S.S. screen and about that which can be held on a mesh U.S.S. screen. A suitable pellet may be obtained by placing the blended mixture in a pelleting press and compacting the mixture under a pressure of at least about 2,000 pounds per square inch. The separated product from the granulating step which is free of undesirable small particles and has a relatively uniform size is eminently suited to be packed into delay tubes to form charged delay elements.

A delay element may be produced by packing a charge of delay fuse composition of the present invention into a tubular member, preferably of a non-sparking metal, for example, aluminum, lead, copper or brass, which is of a size to be received and function as a component in a delay detonator. Generally, the delay tubes found in commercially available delay electric detonators have an inside diameter between about 0.08 and about 0.14 inch. The delay composition is pressed under high pressure in the tube by means of a press pin or other suitable means. Utilization of pressures in the order of about 30,000

- pounds per square inch is quite customary.

The invention may be more specifically illustrated by reference to the following table which shows the results of a series of tests conducted with delay fuse compositions of the present invention. The fuse compositions were compounded by intimately blending the ingredients in a finely divided form in a double cone blender for a period of 16 hours. The blended powder was then pelleted by placing the blend in a pelleting press and applying a pressure of about 12 tons per square inch. The pelleted material was then ground and delay fuse composition having a grain size of between about that which will pass a 20 mesh U.S.S. screen and screened to obtain a sized found for the five detonators was 225 milliseconds and the scatter was 12 milliseconds. Examples 2 through 5 show the results of a series of accelerated aging tests wherein short period delay detonators containing a delay fuse powder having the composition of Example 1 were stored at a temperature of 50 C. for periods of one, two, three and six months. Examples 2 through 19 were carried out in a similar manner to that described for Example 1. The Ti/ Ni alloy shown in Examples 7 through 10 and 14 through 16 contained 70% by weight titanium. The Ti/Ni alloy shown in Examples 17 through 19 con tained 50% by weight titanium.

Table I Delay Composition Delay Time (Milliseconds) Storage Number Example Si Ti/Ni Zn at 50 0., of Det- N 0. months onators KMnOi Mean Scatter Tested (Percent by weight of KMnO4) about that which will be held on a 100 mesh U.S.S. screen. In each test the delay fuse composition was packed into a brass delay tube having a 0.132 inch bore and having a inch length. The granular delay fuse composition was packed into the tube in small increments. Each increment was placed in the tube separately and compacted under about 30,000 pounds per square inch. After compacting each increment had a height of between about .06 and about .07 inch. Nine increments were usually required to be added and compacted to completely fill the delay tube and form a charged delay element. The charged delay elements were then assembled along with the other detonator components into short period delay electric detonators. The assembled short period delay electric detonators were then apportioned into groups for testing. The delay time of some of the detonators in each group was determined immediately. The delay time of the remaining detonators in the group Was determined after an accelerated storage test wherein the detonators were stored at a temperature of 50 C. for periods of from 1 to 6 months. In all of the tests the delay times were determined by utilizing a high speed timer to measure the time elapsing between application of the current to the detonator and the detonation of the detonator. Table I shows the results of a series of such tests. For each example, Table I shows: (1) the composition of the delay fuse composition; (2) the length of storage; (3) the mean delay time; (4) the scatter, i.e., the difference between the minimum and maximum delay times of the detonators in the group tested, and; (5) the number of detonators tested. To illustrate the table, Example I shows the results of five tests that were conducted with detonators having a delay fuse composition compounded of potassium permanganate, powdered zinc in an amount equal to 83% of the weight of the potassium permanganate and silicon in an amount equal to 9.6% of the weight of the potassium permanganate. The mean delay time Table II shows the results of a series of timing tests which were conducted using short period delay detonators which included delay fuse compositions of the present invention. The detonators were assembled from conventional delay detonator components which included in firing order: an ignition means, a charged delay element, a primer charge, and a base charge. The delay elements in each detonator were charged with delay fuse compositions compounded in accordance with the present invention compacted into the tube under a pressure of about 30,000 pounds per square inch. The desired delay times shown in Table II are normal delay intervals utilized in short period delay electric detonators, for example, 25, 50 and milliseconds. The expected burning speed of the present delay compositions when compacted into delay tubes was determined by measuring the time required for a known length of compacted fuse composition to burn, for example, such determination may easily be made from data similar to that shown in Table I. The length of delay fuse composition compacted into the delay tubes of the detonators tested was varied in accord to the expected burning speed to give the desired delay interval. The actual delay interval was determined by connecting the leg wires to a source of electrical current and measuring the time elapsing between the time the current is applied and the time the detonator detonates by means of a high speed timer. To illustrate, Example I of the table shows the results of a series of tests conducted with individual short period delay detonators containing a delay composition of potassium permanganate, zinc and silicon, the amount of zinc being about 83% by weight of the potassium permanganate component and the amount of silicon being about 9.6% by weight of the potassium permanganate component. The desired delay time was 25 milliseconds. The actual delay time found was 23 milliseconds. Each of the other Examples in Table II were conducted in a similar manner.

Table II Delay Composition Actual Delay Time (in milliseconds) Desired Delay Fuse Number Ti/Ni Time Train of Det- Example N 0. Si (70% Zn (in Length onators Ti) milli- (in Tested KMnOi seconds) inches) Mean Scatter (Based on percent by weight of KMI104) The delay fuse compositions of the present invention may contain other ingredients in minor amounts which do not deleteriously affect the compositions for the purposes stated in the specification.

Although the present invention has been described in detail in terms of fuse compositions for blasting detonators, it will be understood that the present compositions are eminently suited to use in delay trains in other types of devices in which accurate timing is required, for example, in the delay fuses used in rockets, artillery shells, grenades, and other ordnance and pyrotechnical devices.

The term consisting essentially of as used in the claims, includes compositions containing the named ingredients and other ingredients which do not deleteriously affect the compositions for the purposes stated in the specification.

What is claimed is:

1. A delay fuse composition consisting essentially of an intimate mixture of finely divided potassium permanganate,

zinc, and

a fuel selected from the group consisting of silicon, and

an alloy of titanium and nickel.

2. A delay fuse composition consisting essentially of an intimate mixture of finely divided potassium permanganate,

zinc, and

silicon.

3. A delay fuse composition consisting essentially of an intimate mixture of finely divided potassium permanganate,

zinc, and

an alloy of titanium and nickel.

4. A delay fuse composition consisting essentially of an intimate mixture of finely divided potassium permanganate,

la first fuel of zinc, and

a second fuel selected trom the group consisting of silicon, and an alloy of titanium and nickel,

the amount of said zinc present ranging from about 55 to about 111% by Weight of the potassium permanganate, and

the amount of said second fuel present hanging from about 3 to about 11% by weight of the potassium permanganate.

5. A delay fuse composition consisting essentially of an intimate mixture of finely divided potassium permanganate zinc, and

silicon,

the amount of zinc present ranging from about 55 to about 111% by weight of the potassium permanganate, and

the amount of silicon present ranging from about 3 to about 11% by weight of the potassium permanganate.

6. A delay fuse composition consisting essentially of an intimate mixture of fine-1y divided potassium permanganate,

zinc, and

an alloy of titanium and nickel,

wherein the amount of zinc present ranging from about 55 to 111% by weight of the potassium permanganate, and

wherein the amount of the alloy of titanium and nickel present is from about 3 to about 11% by weight of the potassium permanganate.

7. The delay fuse composition of claim 6 wherein the alloy of titanium and nickel is comprised of about 70% by weight of titanium.

8. A method of producing a delay fuse composition which comprises the steps of blending finely divided potassium permanganate, zinc, and a fuel selected from the group consisting of silicon and an alloy of titanium and nickel containing between about 40 and about by weight of titanium,

pelleting the mixture obtained from the blending step into a pellet by compacting said mixture under a pressure of at least 2,000 pounds per square inch, and

granulating the pellet to obtain a granulated product.

9. The method described in claim 8 wherein the granulated product is sized to obtain a material having a size of between about that which will pass a 20 mesh U.S.S. screen and about that which will be held on :a mesh U.S.S. screen.

10. A delay fuse composition consisting essentially of an intimate mixture of finely divided potassium permanganate,

zinc, and

an alloy of titanium and nickel,

said alloy of titanium and nickel containing from about 4-0 to about 80% by weight of titanium said zinc is present in an amount ranging from about 55 to about 111% by weight of the potassium permanganate, and

said alloy of titanium and nickel is present in an amount ranging from about 3 to about 11% by weight of the potassium permanganate.

References Cited in the file of this patent UNITED STATES PATENTS ,674 Sosson Jan. 18, 1938 5,371 Burrows et a1 Jan. 2, 1940 2,320,971 Lindsley June 1, 1943 2,457,860 Bennett et al Jan. 4, I949 FOREIGN PATENTS 5 .360 Canada Apr. 1, 1958 

1. A DELAY FUSE COMPOSITION CONSISTING ESSENTIALLY OF AN INTIMATE MIXTURE OF FINELY DIVIDED POTASSIUM PERMANGANATE, ZINC, AND A FUEL SELECTED FROM THE GROUP CONSISTING OF SILICON, AND 